This invention relates to compositions which are useful as antioxidants for organic substances such as rubbers, plastics, oils and greases, and more particularly to rubber latices and vulcanized rubber compositions containing the antioxidant compositions of the invention.
Organic substances such as rubber, plastics, oils and greases essentially are all susceptible to deterioration as a result of prolonged exposure to aging in an oxygen atmosphere. A great deal of effort has been spent, and many antioxidant compositions have been suggested for use in reducing the degradative effects of oxygen on these materials. However, many of the compositions which heretofore have been suggested as antioxidants for these materials have not provided the desired long term stabilization effects possibly because of the tendency of many of the commercially available stabilizers to volatilize when the polymeric products are exposed to elevated temperatures over prolonged periods of time.
Another deficiency of the available antioxidants for stabilizing plastics and rubbers relates to the inability of the antioxidants to resist extraction when the rubbers and plastics are repeatedly brought into contact with aqueous detergent solutions or organic solvents. Suggestions have been made in the prior art for improving the longevity of the stabilization by utilizing antioxidants containing groups which are reactive with a polymer backbone thereby effecting a more permanent chemical bond between the antioxidant and the rubber or plastics. Other techniques which require that the antioxidant be incorporated into the polymer as it is formed also have been suggested.
Nitrile rubbers normally are used when rubber articles are required which have superior resistance to oil and hydrocarbons, good heat stability, abrasion resistance and low permanent set. Therefore, in the normal use of nitrile rubbers, the loss of antioxidants by extraction and/or volatilization is expected but not desirable. Since nitrile rubbers are used widely in automotive and related industries where operating temperatures have risen gradually, the service life of such rubber parts has been affected, and a demand for higher temperature resistant and stable nitrile rubbers has resulted.